Publications by authors named "Beverly D Aagaard"

4 Publications

  • Page 1 of 1

Hemodynamic versus hydrodynamic effects of Guglielmi detachable coils on intra-aneurysmal pressure and flow at varying pulse rate and systemic pressure.

AJNR Am J Neuroradiol 2004 Jun-Jul;25(6):1049-57

Department of Radiology, University of Wisconsin Health Sciences Center, Madison, USA.

Background And Purpose: Alterations in intra-aneurysmal pressure and flow have been observed after treatment with Guglielmi detachable coils (GDCs). We wished to determine whether these changes could be assigned to a hydrodynamic effect of the coils themselves or a compound effect of coils plus thrombus formation.

Methods: Intra-aneurysmal pressure and flow were measured with a 0.014-inch guidewire- mounted transducer in a canine aneurysm in vivo and in vitro before and after treatment with GDCs. Flow was evaluated by using the thermodilution technique. Pressure and flow were also recorded in a bifurcational silicone aneurysm mounted onto a flow phantom during variations in systemic pressure and pulse rate before and following the insertion of GDCs.

Results: The insertion of GDCs induced a reduction in flow that was qualitatively similar when the aneurysm was perfused either by blood (in vivo) or with normal saline (in vitro). Quantitatively, however, flow was reduced less distinctly during perfusion with saline. In the silicone aneurysm, pressure was inversely related to pulse rate and increased with augmenting systemic pressure, whereas flow remained constant regardless of variations in pressure and pulse rate. After GDC placement, reduced flow was dependent on pulse rate but independent of systemic pressure.

Conclusion: GDCs significantly reduced flow even in the absence of thrombus, indicating that they have a purely hydrodynamic effect. In the silicone model, the decrease in intra-aneurysmal flow after coiling relied upon the pulse rate in a manner suggesting the presence of resonance phenomena.
View Article and Find Full Text PDF

Download full-text PDF

October 2004

High-resolution magnetic resonance imaging is a noninvasive method of observing injury and recovery in the peripheral nervous system.

Neurosurgery 2003 Jul;53(1):199-203; discussion 203-4

Department of Radiology, University of Washington School of Medicine, Seattle, Washington 98195, USA.

Objective: Noninvasive observation of degenerating and regenerating peripheral nerves could improve the diagnosis and treatment of nerve injuries. We constructed a novel phased-array radiofrequency coil to permit magnetic resonance imaging (MRI) observation of the sciatic nerve and its target muscles in rats after injury.

Methods: Adult male Lewis rats underwent either crushing (n = 18) or cutting and capping (n = 17) of their right sciatic nerves and then underwent serial MRI. Serial gait track analysis was performed to assess behavioral recovery. Animals from both groups were killed at several time points for histological evaluation of the nerves, with axon counting.

Results: Crushed sciatic nerves demonstrated increased T2-weighted signals, followed by signal normalization as axonal regeneration and behavioral recovery occurred. Cut sciatic nerves prevented from regenerating displayed a prolonged phase of increased signal intensity. Acutely denervated muscles exhibited hyperintense T2-weighted signals, which normalized with reinnervation and behavioral recovery. Chronically denervated muscles demonstrated persistently increased T2-weighted signals and atrophy.

Conclusion: In this study, we demonstrated the ability of MRI to noninvasively monitor injury and recovery in the peripheral nervous system, by demonstrating changes in nerve and muscle that correlated with histological and behavioral evidence of axonal degeneration and regeneration. This study demonstrates the potential of MRI to distinguish traumatic peripheral nerve injuries that recover through axonal regeneration (i.e., axonotmetic grade) from those that do not and therefore require surgical repair (i.e., neurotmetic grade). This diagnostic modality could improve treatment by providing earlier and more accurate diagnoses of nerve damage, as well as reducing the need for exploratory surgery.
View Article and Find Full Text PDF

Download full-text PDF

Source Listing
July 2003

Intraarterially administered verapamil as adjunct therapy for cerebral vasospasm: safety and 2-year experience.

AJNR Am J Neuroradiol 2002 Sep;23(8):1284-90

Department of Radiology, College of Physicians & Surgeons, Columbia University, New York, NY 10032, USA.

Background And Purpose: Despite the widespread use of angioplasty, adjunct chemical therapy is often needed to treat patients with cerebral vasospasm. In this study, we examined the safety of intraarterial administration of verapamil to patients with cerebral vasospasm. We herein summarize our 2-year experience with this treatment.

Methods: We retrospectively reviewed the procedure reports, anesthesia records, clinical charts, and brain images of 29 patients who received intraarterially administered verapamil in 34 procedures for the treatment of vasospasm after subarachnoid hemorrhage from July 1998 to June 2000. The average changes in mean arterial pressure and heart rate were used to measure cardiovascular side effects. The neurologic effects were assessed by angiographic findings, the results of neurologic examinations performed before and after the procedure, and findings of CT of the head.

Results: The average dose of verapamil per patient was 3 +/- 0 mg or 44 +/- 5 mcg/kg. The average changes in mean arterial pressure at 10 and 20 minutes were -5 +/- 1 mm Hg and -2 +/- 1 mm Hg or -3.8 +/- 1.0% and -1.7 +/- 1.1%, respectively. No significant change of heart rate was observed at 10 minutes. The patients showed no sign of increased intracranial pressure by hemodynamic parameters, neurologic examination, or CT of the head. On 10 occasions, when the effect of verapamil infusion was assessed angiographically, there was 44 +/- 9% increase of vessel diameter in the spastic segment. Neurologic improvement was noted after five of 17 procedures when verapamil was used as the sole treatment.

Conclusion: Low dose verapamil is safe when administered intraarterially to patients with cerebral vasospasm. Beneficial effects are achieved in some patients, prompting further study of its efficacy.
View Article and Find Full Text PDF

Download full-text PDF

September 2002

Combined time-resolved and high-spatial-resolution 3D MRA using an extended adaptive acquisition.

J Magn Reson Imaging 2002 Mar;15(3):291-301

Department of Medical Physics, University of Wisconsin, Madison, Wisconsin, USA.

Purpose: To combine the benefits of time-resolved dynamic imaging and single elliptical centric acquisitions in a reasonable scan time.

Materials And Methods: A time series of images with moderate spatial resolution was acquired using the 3D Time-Resolved Imaging of Contrast KineticS (3D TRICKS) technique with elliptical centric encoding during contrast arrival. Following venous opacification, a complete large centrically encoded k-space volume was acquired. The high-spatial-frequency portions of this volume were combined with a 3D TRICKS time frame to form a high-resolution image. An additional single image is formed by suppressing background and signal averaging all acquired data, including post-venous low-spatial-frequency data. For this image, 2D temporal correlation analysis is used to suppress low-spatial-frequency vein contributions. Arrival time and spatial correlations are used to suppress background.

Results: The 3D TRICKS time frame may be selected to ensure a combined high-resolution image that has optimal central k-space sampling for any vascular region. The single image formed by signal averaging all acquired data has increased contrast-to-noise (CNR) and signal-to-noise (SNR) ratios.

Conclusion: The advantages of time-resolved and high-spatial-resolution imaging were combined using an extended dual-phase acquisition. Some SNR and CNR gain was achieved by signal averaging. This process is facilitated by background and vein suppression.
View Article and Find Full Text PDF

Download full-text PDF

Source Listing
March 2002